Mixed base lubricating greases



, Patented July 4, 1950 MIXED BASE. LUBRICATIN G GREASES Arnold J.Morway, Clark Township, Union County, and Rosemary OHalloran, Elizabeth,N. J., assignors'to Standard Oil Development- Company, a corporation ofDelaware No Drawing. Application June 5, 1948, Serial No. 31,398

4 Claims. (Cl. 252- 10) The" resent invention sass to' mixed" baselubricating "greases "and particularly to sodabarium soap greases whichareparticularly suited for the lubrication of high speed anti-frictionbearings over a broad temperature range. The invention relatesfurthertoa process for producing-greases of'thetype referred to and to theimprovement of viscosity-temperature characteristics of such greases;

In U. S. 'Patent'NO. 2,245,702 to Morway, one

of the present inventors; there is described a mixed base greaseprepared fromthe mixed soaps of soda and baryta which has been foundfairly satisfactory'for the lubrication of anti-friction bearings. Thecompositiondescribed in said patent, however, has certain deficienciesin that it is not usefulv over ,as wide a temperature range as may bedesire'd and its viscosity and consistency vary considerably with widechanges in temperature. The greasedescribed in said patent contains'aslight'excess of alkali, for example from 0.05 to 0.3%. The compositiondescribed therein I becomesrfibrous at temperatures of about 230 to 240F. v

It has now been found that unexpected improvements in mixed soda-bariumgrease may be obtained by employing fatty acids of average lowermolecular weight than the acids used in the prior art and by employmentof a base lubricating oil of high viscosity index. In addition, it

has been found that if the finished grease contains a small amount offree acid rather than free alkali as in the aforesaid patent, a. changein physical structure of the grease is permitted at high temperatureswhich makes the lubricant suitable for anti-friction bearings running athigh speeds and at elevated temperatures.

It is-well known that most lubricating greases pass through a change ofphase at a temperature in the approximate vicinity of the melting pointof the fat or fatty acid from which the thickening soap is prepared. Thephase'change occurring at this point, i. e. the uni-dimensional meltingpoint of the soap, is slight. However, at higher temperaturesv anotherphase change occurs which is due toincreased thermal energy in the soaplattice and is called the bi-dimensional melting point. phenomenon bywhich" a soap structure which exists in threedimensions breaksdowzr inthe By the latter expression is meant the second of such dimensions. Atsuchca phase:

change or transition point, lubricating greases lose their short fiberedsmooth structure andbecome very fibrous and rubbery in character.

If the change in phase referred to above occurs in a lubricating greasebelow the desired operating temperature, the grease is not a goodlubricant. Since anti-friction bearings under many" operating conditionsattain temperatures considerably higher than the normal transition orphase change temperature of greases, it is desirable to change thetransition temperature. The present invention is basedupon the discoverythat this can be accomplished by using a fatty acid of shorter chainlength, or lower molecular weight, in producing the grease-forming soap.Apparently such a reduction in the molecular weight or chain length alsodecreases the solvency of the soap in the mineral oil. In addition, bythe use of more aliphatic type mineral oils, i. e.

' paraifinic or predominantly paralfinic as distinguished fromnaphthenic or aromatic, the soap solvency in the oil is furtherdecreased. This further raises the temperature at which phase change ortransition takes place. These results.

can be obtained without so far reducing solvency of the mineral oil forthe soaps that the soaps will separate from the oil on cooling.

The use of a high viscosity index oil, that is an oil that is moreparaifinic than customarily used in grease manufacture, not only raisesthe transition temperature but also gives a product which has bettertemperature-viscosity relationship. The latter is an obvious advantageof the use of oil of high viscosity index but the former is quiteunexpected and is contrary to the general custom of using low viscosityindexoils for most lubricating greases. As a result, lubricants,

prepared according to the present invention may be used at extremely lowtemperatures as Well as at very high temperatures, comparativelyspeaking.

By employing the three factors mentioned.-

above, namely, the shorter average length of the fatty acid chain, abase lubricating oil of high viscosity index, and a slight excess ofacidity as be obtainedwith relatively less soap. Thus the soap contentmay be as low as 3. or 4% although Tit ma'ygalso'go as high as 25 "or.30%rby'weight;

based on the finished grease, if a very stiif lubricant is desired.These greases obviously have more body at higher temperatures and lessat lower temperatures because of the high viscosity index oil used andthey give outstanding performance on the high temperature-high speedspindle test. Such greases have excellent shear stability and'do notbreak down upon severe mechanical working.

EXAll/[PLE As one example of a grease made according to the presentinvention, the following formula was employed:

12.50% hydrogenated fish oil fatty acids (predominately palmitic acid)1.70% sodium hydroxide 0.78% barium hydroxide octahydrate 0.40%phenyl-alpha naphthylamine antioxidant 71.87% extracted Panhandledistillate (150 vis./

100, SUS) I 12.80% extractedCoastal distillate (80 via/100,

SUS)

concentrate was heated further as the remainder of the lubricating oilwas added slowly. This was continued until the soap was completelydispersed in the mineral oil at a temperature of between 375 and 425 F.The grease was then poured into pans for cooling and homogenized to thedesired consistency at room temperatures.

Although the foregoing is a desirable method for preparing greases ofthe mixed soda-barium type, they can easily be prepared by other wellknown methods. The temperatures employed may be as low as 350 or as highas 500 F. or more if desired. Hydrogenated fish oil acids which have anaverage composition of less than 18 carbon atoms per molecule and morethan 14 are very satisfactory but other acids may be used if desired. Ingeneral, the fatty acids having 14 to 18 carbon atoms and even slightlyhigher acids in minor proportions are quite suitable, but it isimportant that the average should be at least slightly less than thecomposition of stearic acid, 1. e. 18 carbon atoms. Otherwise, oilsolubility of the soaps is too great to realize the full benefits ofthis invention. Similarly, if the average composition is C14 or lower,the oil insolubility is too great. Simple acids such as lauric,myristic, or palmitic may be used in mixtures with each other or withstearic acid as desired to obtain the proper average.

The grease in the example, as noted above, was prepared from a base oilcomposed predominantly of extracted Panhandle distillate with a smallamount of extracted Coastal distillate. The viscosity index of thecombined oils was about 93.

For comparative purposes, two similar compositions were prepared fromother oils and subjected to high speed spindle tests at a temperature of250 F. The first was prepared from a straight Coastal distillate havinga viscosity index of 50 and the second from a Rodessa distillate havinga viscosity index of 113.- The performance data are shown in Table 1.

TABLE 1 Performance of Soda-Barl- The spindle test apparatus used inthese runs is the ABEC-NLGI Committee Test as described in theCommittees Technical Bulletin No. 5. It consists of a 204 type ballbearing mounted on a belt-driven spindle under a thrust load of 14-15 D.s. i. This is operated at 250 F. and 10,000 R. P. M. on a 22-hour cycle,(2 hours at room temperature) until failure occurs. Failure 00- curswhen the bearing is running under such friction that the operatingtemperature rises 25 F.,

TABLE 2 Performance of Soda-BariumGi-eases at 250 F.

Mineral Oil Panhandle Rodessa Dis- Distillate tillate Via/210 F., SUS .u44 44 Viscosity Index 113 Hrs. Spindle Life at 10,000. RPM 1, 874 500-1,100

In general, the low temperature properties of a grease are governed byits soap content, and the pour point and viscosity (at the testtemperature) of its mineral oil. Therefore, improve ments in performancemay be obtained by lowering any of these factors. Dewaxing, or dilutionof the mineral oil, or lowering the soap content are all possibilities.

Dewaxing the Panhandle distillate from its original +30 F. pour point to0 F, pour point definitely improves its low temperature characteristicsat -40 F., 17.4 sec./rev., as compared to 37.1 sec/rev. However, thisgrease did not have as good high temperature characteristics as theundewaxed stock as shown in Table 3.

es ae. ce ta niae .l. see .t ah

appease .iqua tie rofsthis aphan ees gcls .arap *such a nat e .:tha--.:,th.e ch se. :wi x ctediGoast l1d prove -.th ig ow t mpera urewmperti sm atu e. p rfo m mthi way ae easeqfjan ll n co i ation:;f&popeti anzbe =p --du zed-. 15

I The comparative propelities of a straight Panale rd ti lat and, 9Panha dle ldi lla eS Wi-th.l %.Q ;C a le L, arezshow an f am 1 It w ll-bnot tena tisuzlarly that the .;1.ow m e tur torqu l b ntiel law-er .a ni "mixe oi lub c the. st a h P h n rd l t ser as sced-bdridmergdsesPanhandle Panhandle Distillate Distillate .-l- Coastal Distillatemessiah-hydrogen eee s a ii h high wi ld a ue f, t

rodu d "w th; b ly bo r 14%... .59 l 5. 1 abla a a dagils ie ver- .agecharn lengths are used to form .the -soaps.

easerwith u materia lyafiect z ez h m-- uc :a c mpes tion wa a d ti at.a inth E ed x qd rba z am. .g' es .iof t ,1 ven ie ipr ductsiofaqprqximately the same .-consistency' Yes This of advantage because ]-,alarge soap .con-

tent adversely afiects the low temperature performanceofithe'grease-aindicated by atorque off37.1 for a grease "containing 15.6% soap ascompared with torqueof" 23:9=for the same type The ue-eer e "minimumsoap content ,is advantageous for reasons of economy as w'ell as forimproved lowtemperature performance. By

she iattyacid a e .used-morerso p i e ui to give the grease a stablestructure. Also, such soaps increase the torque resistance of the greaseat low temperature, as shown in Table 4.

Hydrogenated fish oil acids of different types vary in composition asregards the chain length of their constituents. Thus one commercialfatty acid marketed as 51-HO contained 15.8%.

myristic (C14) acid, 56.6% palmitic (C15) acid,

20.4% stearic (C18) acid, 3.4% arachidic (C20) acidand 1.3% behenic(C22) acid. Another, sold under the trade name Hydrofol 51 contained8.5% myristic, 35.2% palmitic, 28.2% stearic and i 15.0% and 8.8%,respectively, of arachidic and behenic acids. The former was used in theex- .famplermbove, :w'hereas the 5 as, greater torque, when used in thesrl ttermasxusedinsth greases iofifables. l p Q .i

greases prepared with soaps of higher .fatty s, re. acidsbf longeraverage c'n ai .01 lout the .difference in oils employed is also-pigspme impbr'mnee, as indicated below in Table..5.

It should be noted that -grea'sescontainin'g as are-too soft f for useat elevated temperatures bec us s P9 1 hea "st i ib Thesis? {of .655ontaine abp 1 o u aps Extracted RoQessa. Distillate i were YOoastal i tl a mesa-an g "It smite kite-d thaeth "-respective-minera1 one er"Table- 5 "had approximately the same viscosity letrg o sag t*trieaqdess distillate had a rnuch "higheryiscositytindex. p h

A th u h .th gere se .01 t i in c prepa e wit emal un sq ex ss fre eflinity as; well as free facidity, itghas been found tha t e pr enc o agal iamc n gireefatt acid substantiall limproves thehigh tempera- ;tureiperforman of the product, [without detrifment to "the Qoxidationresistance or'shear 1 stabil ity. Evidently t, ireeifatty acidihas.somejsQ1- iri cy-.efie tm v etm th si ase rom e n rubbery at the hightest temperature. The 'data 0 in Tablefishow thesuperiorlife of variousgreases il ydrnfol 5. :a ds, beingacida dalkaline;

spe i ly.

' meme Hig h etemperatune :performafic of ws odabarium v:- :grea'sesFrom thezforegQing-it 'vwill .bei'seensthat mixed base greases havingexcellent properties of shear stability, resistance to oxidation, yieldvalues, and high temperature structure stability may be produced fromthe sodium-barium soaps of relatively low molecular weight fatty acids.As suggested above, the extracted Panhandle distillates are particularlydesirable as base lubricating oils, but the invention is not limited tothe use of such oils. In some cases, it is desirable to add some Coastalstock to cut back the extracted Panhandle becauseof the high pour pointof the Panhandle. A mixture or blend having approximately the followingcharacteristics appears to be highly suita- 'ble "as a base'forth'egreases of this invention, but

the invention is not by any meanslimited thereto.

via 1009'n.,,sus', 143.1 Via/210 n, s s' -1 42.5 Vis. index H 92 Flash-F 385 Pour ..Q Y V Y F +25 In general a lubricating grease prepared fromoils of-;fair1y high-viscosityindex, for-example 80 to 125,-thickenedwith-5 or 6 to 25 .or. 30%, prefer- The limitations stated therein areasodiumbarium soap weight ratio of from 1 to 1, to about 10 to 1 whichcorresponds to mol ratios of from about 1.2 to 1 to about 12 to 1. Thelimits'in the case of the present type of compositions are greater,especially with regard to the upper limit, a

theoverall range being between about 1 to 1 and 30 to 1, on a sodiumsoap/barium soap. mol ratio basis. Preferably the mol ratio is in therange from about 15 to-1 to,about to 1. The preferred range inthepresent compositions is therefore considerably higher than the upperlimit of the prior art compositions, which differ howeverinfse'veralother ways. Especially suitable is a mol ratio from about 1'2to 1 to. about 19 to 1.

. The excess quantity of acid maybe varied i somewhat but should bekeptrather ,low. In general it should be fromas low as 0.01% and ingeneral from 0.05 to 0.5% by weight calculated as free oleic acid.

I It will be understoodthatthe greases prepared according 'to thisinvention may contain conventional additives such as antioxidants,tackiness agents, extreme pressure additives, corrosion inhibitors, andother materials such as are well known in the art. It is generallypreferred toinclude a small amount of a suitable antioxidant such asphenyl alpha napthylamine or phenyl beta naphthylamine and the like,although such material are not always required. When included theyshould be added in proportions of 0.1 to about 1% by weight,'based'onthe composition, 04 or 0.5% usuallybeing preferred. In general, theoil composition, which may include these additives and is referred togenerally as lubricating oil in the claims should have V. I. of at least80 and preferably 85 to 115. The

oil will preferably comprise 75 to 94%. of the composition and the soapfrom about 6 to 25%,

although these limit may be exceeded forspecific purposes.

What is claimed is:

lated as me oleic 'acid.

consistingessentially or aminer'al base meacating oil having a viscosityindex of at least '80 thickened to a grease consistency with a mixedsodium-barium soap of fatty acid having an average of less than 18carbon atoms, wherein the molar ratio of soda soap to barium soap isbetween 1 to 1 and 30'to '1 said grease containing a slight excess ofsaid fatty acid suflicient to give a free acidity of 0.01 to 0.5% byweight, calcu- 2. A lubricating grease composition consistingessentially of to 94% mineral base lubricating oil having a viscosity of50 to 500 SSU at 100 *F. and a viscosityindex of between and- 115,'and 6to 25% of a mixed sodium-barium soap ofhyfdrogenated"'fish' oil acidshaving an average molecular composition of less than 18 carbon atoms andatleast 14 atoms, wherein" the molar ratioof'soda soap to barium soap isbetween lto 1 and 30 to 1 said grease having a sufiicient excess of saidacids to give v.a free acidity of 0.05 to 0.5% by weight, calculated asoleic acid.

3. A lubricating grease consisting" essentially of ,80 to mineral baselubricating oil having a viscosity index of at least 80, about 10 to 20%of mixed sodium-barium soaps of aliphatic ,car.-

'boxylic acids having an average composition of more than 14 and lessthan 18 carbon atoms, wherein the molar ratio of soda soap to bariumsoap is between 1 to 1 and '30 to 1 about 0.1 to 1% of an antioxidant,said grease having a suflic'ient excess of said acids to give-a freeacidity of about to 0.5% by weight, calculated as free oleic 4; .Alubricating grease composition consisting REFERENCES CITED h Thefollowing references are of record-in the file 'of this patent:

UNITED STATES PATENTS Number Name Date 2,005,553 Miller June 18, 19352,245;702f Morway June'1'7, 1941 2,318,847 Flint et a1. May 11, 19432,449,312 Murray et al Sept. 14; 1948 2,451,032 Morway et al. f Oct.12,1948 2,468,099 Morway Apr. 26, 1949 2,487,080

Swenson Nov. 8,1949

1. AN ANTI-FRICTION BEARING LUBRICATING GREASE CONSISTING ESSENTIALLY OFA MINERAL BASE LUBRICATING OIL HAVING A VISCOSITY INDEX OF AT LEAST 80THICKENED TO A GREASE CONSISTENCY WITH A MIXED SODIUM-BARIUM SOAP OFFATTY ACID HAVING AN AVERAGE OF LESS THAN 18 CARBON ATOMS, WHEREIN THEMOLAR RATIO OF SODA SOAP TO BARIUM SOAP IS BETWEEN 1 TO 1 AND 30 TO 1SAID GREASE CONTAINING A SLIGHT EXCESS OF SAID FATTY ACID SUFFICIENT TOGIVE A FREE ACIDITY OF 0.01 TO 0.5% BY WEIGHT, CALCULATED AS FREE OLEICACID.